A current trend in merchandising is to present products in their authentic state, not imitations or representations, thus increasing their visual appeal. This is particularly difficult to accomplish, however, with ice cream and other frozen foods which, when exposed for viewing purposes, will degrade in quality and appearance.
Low temperature cabinets for displaying and merchandising frozen foods have been manufactured for many years. With these cabinets, however, exposed products, especially ice-cream cream products, quickly deteriorate. This occurs because frozen dairy products contain a high concentration of water, and water molecules diffuse through and migrate out of the product. This diffusion is driven by vapor pressure differences which relate to temperatures in general, and dew point temperatures in particular. The greater the difference between the dew point of the product and its surroundings, the greater the diffusion rate and moisture loss. Moisture loss can be further accelerated if the air surrounding the product is in motion, as it is in a forced convection system. Migration of moisture from the frozen product degrades product quality, and causes the product to lose visual appeal.
Display cases typically use a fan to circulate cold air within the display case and over the frozen product. The air is chilled by a direct expansion refrigeration coil whose temperature may be as much as forty degrees below the cabinet air temperature. The dew point of the air is nearly equal to the surface temperature of the coil, while the dew point of the product is the same as the air temperature. The difference between the dew points results in a high rate of moisture loss from the frozen product.
Therefore, there exists a need in the art for a low temperature display device which permits a consumer to directly view a frozen product to be sold while the product is maintained at a below freezing temperature. There is also a need in the art for such a display device in which food may be maintained for long periods of time without substantial reduction in moisture content, quality, consistency, or appearance.